1. Field of the Invention
This invention relates to a rear conversion lens apparatus for focusing which can be mounted to a lens for a single lens reflex camera and can be versatilely used.
2. Description of the Prior Art
Various lenses capable of being automatically focused have already been commercialized in single lens reflex camera, but all of them are exclusive lenses capable of automatically focusing only particular lenses and therefore have no versatility and moreover have been expensive.
Therefore, the construction of a focusing converter in which a lens system exclusively for focusing is mounted beween an objective lens and a camera body to enable automatic focusing to be versatilely accomplished is proposed, for example, by Japanese Laid-Open Patent Application No. 28133/1979, but this has not withstood practical use. That is, in order that a converter may be mountable to all objective lenses, it must be a compact one mountable not only to great aperture ratio objective lenses but also to objective lenses having a short back focal length and moreover must maintain an excellent imaging performance, and it has been very difficult to design a converter which will satisfy all of these conditions.